WASHINGTON (AP) — Average long-term U.S. mortgage rates fell this week, retreating from high levels for the year amid economic turbulence overseas. The lower rates brought an incentive for prospective purchasers toward the end of the spring home buying season.

Mortgage giant Freddie Mac said Thursday the average rate on a 30-year fixed-rate mortgage declined to 4.04 percent this week from 4.08 percent a week earlier. The rate on 15-year fixed-rate mortgages eased to 3.20 percent from 3.24 percent.

Markets around the world have been nervously watching tumult and a nearly month-long slide in China's stock markets, and Greece's economic crisis as it tries to negotiate a rescue from its European partners. That has pushed investors to seek safety in U.S. Treasury bonds, pushing interest rates lower.

Bond yields for Treasurys have been pushed lower by the rise in bond prices. The yield on the key 10-year Treasury note dropped to 2.20 percent Wednesday from 2.42 percent a week earlier. Mortgage rates often follow the yield on the 10-year note. It traded at 2.27 percent Thursday morning.

To calculate average mortgage rates, Freddie Mac surveys lenders across the country at the beginning of each week. The average doesn't include extra fees, known as points, which most borrowers must pay to get the lowest rates. One point equals 1 percent of the loan amount.

The average fee for a 30-year mortgage was unchanged from last week at 0.6 point. The fee for a 15-year loan fell to 0.5 point from 0.6 point.

The average rate on five-year adjustable-rate mortgages fell to 2.93 percent from 2.99 percent; the fee remained at 0.4 point. The average rate on one-year ARMs declined to 2.50 percent from 2.52 percent; the fee was stable at 0.3 point.